A quick perusal of the 2010 Cubs sortable schedule today provided some clues as to when they will be on Fox (Saturdays) and ESPN (Sunday nights). Follow me past the jump for the dates.
Based on game times listed on the schedule, the following Saturday games will be on Fox, game time 3:10 pm CDT:
Saturday, May 29, vs. Cardinals Saturday, June 12, vs. White Sox Saturday, July 10, at Dodgers Saturday, August 21, vs. Braves Saturday, September 4, vs. Mets
Each team is allowed a maximum of eight appearances on Fox Saturday games -- the following are listed as "TBD" and some of them will probably wind up as Fox games:
Saturday, May 22, at Rangers Saturday, June 26, at White Sox Saturday, July 31, at Rockies Saturday, August 14, at Cardinals Saturday, September 25, at Cardinals
It'll probably be the White Sox and Cardinals games -- the Rockies and Rangers have NO starting times listed yet.
The following Sunday games are already listed with evening start times, meaning they'll be on ESPN:
Sunday, July 11, at Dodgers Sunday, July 18, vs. Phillies
The July 18 game has a 5:05 starting time -- that's the Sunday ESPN does the ESPY awards, so whatever game is on that night has to start two hours earlier than usual. That'll make for some interesting right field shadows.
The following Sunday games are listed as "TBD" -- each team can appear five times max on Sunday night, so since the Cubs are a pretty good draw for ESPN, probably three of these will wind up as night games:
Sunday, May 23, at Rangers Sunday, June 13, vs. White Sox Sunday, June 20, vs. Angels Sunday, June 27, at White Sox Sunday, July 25, vs. Cardinals Sunday, August 1, at Rockies Sunday, August 22, vs. Braves Sunday, September 25, vs. Cardinals
You can probably eliminate the Rockies and Rangers again, as they have no starting times listed at all; Cardinals and White Sox Sunday dates with the Cubs have been good draws for ESPN in the past. That 9/25 date is the last regular season home game. One good thing about the 2010 night game schedule: there are only two home night games in April (vs. the Nationals on April 26 and 27), minimizing the time the team will have to contend with cold nighttime weather early in the season. The next night game after the two vs. the Nats is on May 10 vs. the Marlins. I've updated the BCB tentative 2010 Cubs schedule with all these times; it can be found permanently on the left sidebar.